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Parameter Optimization for Predicting Soil Water Movement under Crop Residue Cover

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 54(6): 2029-2035. (doi: 10.13031/2013.40661) @2011
Authors:   P. N. Singh, J. P. Mitchell, W. W. Wallender
Keywords:   Crop residue, Evaporation, Optimization, Modeling, Soil water content

Plant residue on the soil surface is considered useful for reducing the evaporation component of crop evapotranspiration. In contrast to soil, the upward movement of water through the plant residue layer is predominantly in the vapor phase rather than the liquid phase. Because of this difference in the mechanism of water movement, physically based numerical models that simulate liquid-dominated water movement in the soil profile have not been tested for water movement through residue. In this article, a new methodology is presented in which the crop residue layer is replaced with a hydraulically equivalent soil layer (ESL), thereby allowing the use of a numerical model, Hydrus-1D, to simulate the changes in soil moisture in a residue-covered production system. Parameter optimization software, PEST, was used to characterize the unsaturated hydraulic function of the ESL. The data for calibrating and validating the model were collected from two different studies in 2010 at the University of California West Side Research and Extension Center in Five Points, California. The simulated soil water content in the profile under the ESL matched the measured soil water content under crop residue cover with RMSE values of 0.004 to 0.013 cm3 cm-3 for calibration and 0.001 to 0.019 cm3 cm-3 for validation. Parameter optimization of the ESL provides a new tool to allow the use of a physically based model such as Hydrus-1D to simulate the many complex interactions between the soil, crop residue, and atmosphere. The methodology may need further validation in different soil, mulch, and climatic conditions. In future research, the effect of crop residue on evaporation for a crop system will be quantified for different growth periods, and efficient irrigation management protocols will be designed to reduce the evaporation component of crop evapotranspiration.

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